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Disclosure to Promote the Right To Information 

Whereas the Parliament of India has set out to provide a practical regime of right to 
information for citizens to secure access to information under the control of public authorities, 
in order to promote transparency and accountability in the working of every public authority, 
and whereas the attached publication of the Bureau of Indian Standards is of particular interest 
to the public, particularly disadvantaged communities and those engaged in the pursuit of 
education and knowledge, the attached public safety standard is made available to promote the 
timely dissemination of this information in an accurate manner to the public. 

Mazdoor Kisan Shakti Sangathan 
"The Right to Information, The Right to Live" 

IS 15493 (2004, Reaffirmed 2010) : Gaseous Fire 
Extinguishing Systems— General Requirements. ICS 13.220.10 

Jawaharlal Nehru 
'Step Out From the Old to the New' 

■K^y / 1 juaaaws^fea rs^^TTF^ 

2*S< W I *>S*V2^NK^ 


Satyanarayan Gangaram Pitroda 
Invent a New India Using Knowledge 

Bhartrhari — Nitisatakam 
"Knowledge is such a treasure which cannot be stolen" 



(Reaffirmed 2010) 

v IS 15493: 2004 

Indian Standard 


ICS 13.220. 10 

©BIS 2004 


NEW DELHI 110002 

August 2004 Price Gronp 10 

Fire Fighting Sectional Committee, CED 22 


i his Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the 
Fire Fighting Sectional Committee had been approved by the Civil Engineering Division Council. 

Attention is drawn to Montreal Protocol on substances that deplete the ozone layer. As India is a signatory 
to the Protocol, country programme was drafted wherein suitable alternative clean agents have been identified 
in the place of Halons 1301 and 1211. As per the approved programme, this standard has been formulated for 
the identified alternatives. The agents covered in this standard are thus introduced in response to international 
restrictions on the production of certain Halon fire extinguishing agents under the Protocol signed in 1992, as 

it is important that the fire protection of a building or plant be considered as a whole. Gaseous clean agent 
systems form only a part, though an important part, of the available facilities, but it should not be assumed that 
their adoption necessarily removes the need to consider supplementary measures, such as the provision of portable 
tire extinguishers or other mobile appliances for first aid or emergency use, or to deal with special hazards. 

Gaseous fire suppression systems covered in these Indian Standards are designed to provide a supply of 
gaseous extinguishing medium for the extinction of fire involving high value assets. 

Gaseous clean agents have for many years been a recognized effective medium for the extinction of flammable 
liquid fires and tires in the presence of electrical and ordinary Class A hazards, but it should not be forgotten, in 
the planning of comprehensive schemes, that there may be hazards for which these mediums are not suitable, or 
that in certain circumstances or situations there may be dangers in their use requiring special precautions. These 
difficulties have been addressed in this standard. 

Various methods of supplying clean agent to, and applying it at, the required point of discharge for fire extinction 
have been developed in recent years, and there is a need for dissemination of information on established 
systems and methods. This standard has been prepared to meet this need. New requirements to eliminate the 
need to release clean agents during testing and commissioning procedures are included. These are linked to 

the inclusion of enclosure integrity testing. 

The requirements of this Indian Standard are made in the light of the best technical data available at the 
time of drafting this standard but, since a wide field is. covered, it has been impracticable to consider every 
possible factor or circumstance that might affect implementation of the recommendations. 

It has been assumed in the preparation of this Indian Standard that the execution of its provisions is 
entrusted to people appropriately qualified and experienced in the specification, design, installation, testing, 
approval, inspection, operation and maintenance of systems and equipment, for whose guidance it has been 
prepared, and who can be expected to exercise a duty of care to avoid unnecessary release of clean agent. 

Specific requirements and advice on these matters can be obtained from the appropriate manufacturer of the 
clean agent or the extinguishing system. Information may also be sought from the appropriate fire authority, 
the health and safety authorities and insurers. In addition, reference should be made as necessary to other 
statutory regulations. 

It is essential that fire equipment be carefully maintained to ensure instant readiness when required. Routine 
maintenance is liable to be overlooked or given insufficient attention by the owner of the system. The importance 
of maintenance cannot be too highly emphasized. 

For the purpose of deciding whether a particular requirement of this standard is complied with, the final 
value, observed or calculated, expressing the result. of a test or analysis, shall be rounded off in accordance 
with IS 2 : 1960 'Rules for rounding off numerical values (revised )\ The number of significant places retained 
in the rounded off value should be the same as that of the specified value in this standard. 

IS 15493 : 2004 

Indian Standard 



This standard specifies provisions and 
recommendations for general requirements, type of 
clean agent and their containers, container arrangement, 
distribution systems, such as piping, nozzles, pipe 
supports, alarm system, type of enclosure etc. 


1 This standard covers the general requirements 
applicable to total Hooding clean agent systems like 
Halo-Carbon agents and inert gas agents. In addition, 
individual requirements for each type of clean agent 
system are covered under separate standards. Detailed 
design guidelines are specified in other standards. Hence 
before designing a protection with a particular clean 
agent, both the standards should be read together. Wherever 
there is a difference, the individual standard takes 

2 This standard prescribes minimum requirements for 
total flooding clean agent fire/extinguishing systems. 
Protection with carbon dioxide is not covered in this 

3 Nothing in this standard is intended to restrict new 
technologies or alternate arrangements provided the level 
of safety prescribed by this standard is not diluted. 


The standards listed in Annex A contain provisions 
which through reference in this text, constitute 
provisions of this standard. At the time of publication, 
the editions indicated were valid. All standards are 
subject to revision and the parties to agreements 
based on this standard are encouraged to apply the 
most recent editions of the standards indicated 
in Annex A. 


For the purpose of this standard, the following 
definitions shall apply. 

3.1 Adjusted Minimum Design Quantity 

( AMDQ ) — The minimum design quantity of agent 
that has been adjusted in consideration of design 

3.2 Approved — Acceptable to a relevant authority. 
In determining the capability of the installations, 
the authorities may base their acceptance with 
appropriate standards. The design and system 
approval shall be from national or international 
approving authority or lab of repute. 

3.3 Authority — The organization, office or individual 

responsible for approving installation or equipment 
or a procedure. 

3.4 Automatic — Performing a function without the 
necessity of human intervention. 

3.5 Automatic/Manual Switch — A means of 
converting the system from automatic to manual 
( manual override ) and vice-versa. 

3.6 Class A Fires — Fire in ordinary combustible 
materials, such as wood, cloth, paper, rubber, many 
plastics, electrical and electronic hazards without 
any flammable fluid or gas. 

3.7 Class B Fires — Fire in flammable liquids, 
oils, greases, tars, oil-based paints, lacquers and 
the like. 

3.8 Clean Agent — Electrically non-conducting, 
vapourizing, or gaseous clean agent that does not 
leave a residue upon evaporation. The word agent 
wherever appearing in this document shall mean as 
clean agent. 

3.9 Clearance — The air distance between clean 
agent equipment, including piping and nozzles 
and unenclosed or uninsulated live electrical 
components at other than ground potential. 

3.10 Containers — A cylinder or other vessels used 
to store the clean agent. 

3.11 Container Discharge Vaive — A valve directly 
connected to a container which when actuated 
releases the clean agent into the distribution 

3.12 Control Device — A device to control the sequence 
of events leading to the release of clean agent. 

3.13 Concentration 

3.13.1 Design Concentration — The concentration 
( including safety factor ) of the clean agent 
necessary to extinguish a fire of a particular fuel. 

3.13.2 Extinguishing Concentration — The 
concentration ( without safety factor ) of the 
agent necessary to extinguish a flame of a particular 
fuel at atmospheric pressure. 

3.13.3 Hazardous Concentration — The 
concentration that exceeds the LOAEL 
( see 3.28 ) for the agent used. 

IS 15493 : 2004 

3.13.4 Injected Concentration — The concentration 
of the agent necessary to develop under free efflux 
conditions the required design concentration. 

3.13.5 Maximum Concentration — The concentration 
achieved from the actual clean agent quantity at the 
maximum ambient temperature. 

3.13.6 Residual Oxygen Concentration — The 
resulting concentration of oxygen achieved within 
a protected area after the discharge of agent into 

the area, 

3. 1 4 Design Factor ( DF ) — A fraction of the agent 
minimum design quantity ( MDQ ) added thereto 
deemed appropriate due to a specific feature of the 
protection application or design of the suppression 

3.15 Directional Valve — A device for controlling 
the passage of the clean agent from a supply 
manifold and directed to pre-selected area(s) of 

3.16 Discharge Inhibit Switch — A manually 
operated switch that prevents the automatic discharge 
of the clean agent. 

3.17 Distribution System — All the pipe work 
and Fittings downstream of any container discharge 


3.18 Engineered Systems — A system in which 
the supply of the clean agent stored centrally is 
discharged through a system of pipe and nozzles in 
which the size of each section of pipe and nozzle 
orifice has been calculated in accordance with 
relevant clauses of this standard. The design flow 
rates from nozzles may vary according to the design 
requirements of the hazard. 

3.19 Fill Density — The mass of gaseous agent per 
unit volume of container ( kg/m 3 ). 

3.20 Final Design Quantity ( FDQ ) — A quantity 
of agent determined from the agent minimum 
design quantity as adjusted to account for design 
factors and pressure adjustment. 

3.21 Flooding Quantity — Mass or volume of clean 
agent required to achieve the design concentration 
within the protected volume within the specified 
discharge time. 

3.22 Gross Volume — The volume enclosed by 
the building elements around the protected 
enclosure, less the volume of any permanent 
impermeable building elements within the 

3.23 Holding Time — Period of time during which a 
concentration of clean agent greater than the fire 

extinguishing concentration surrounds the hazard. 

3.24 Inert Gas Agent — A clean agent that contains 
as primary components one or more of the gases 

3.25 Inerting — The prevention of reignition of 
a flammable or explosive atmosphere by establishing 
a suitable concentration of the clean agent. 

3.26 Liquefied Gas — A gas or gas mixture ( normally 
a halocarbon ) which is liquid at the container 
pressurization level at room temperature ( 20°C ). 

3.27 Lock-Off Valve — A mechanically operated 
device which prevents a clean agent from being 
discharged through distribution pipe work to the 
protected area. 

3.28 Lowest Observed Adverse Effect Level 

( LOAEL ) — The lowest concentration of clean agent 
at which an adverse toxicological or physiological 
effect has been observed. 

3.29 Manual — Requires a human intervention to 
accomplish a function or task. 

3.30 Maximum Working Pressure — Equilibrium 
pressure within a cylinder at the maximum working 
temperature. For liquefied gases, this is at maximum 
fill density and may include super-pressurization, if 

3.31 Minimum Design Quantity ( MDQ ) — The 

quantity of agent required to achieve the calculated 
minimum design concentration. 

3.32 Monitoring — The supervision of the operating 
integrity of an electrical, mechanical, pneumatic or 
hydraulic control feature of a system. 

3.33 No Observed Adverse Effect Level 

( NOAEL ) — The highest concentration of a clean 
agent at which no adverse toxicological or 
physiological effect has been observed. 

3.34 Non-liquefied Gas — Gas or gas mixture 
which, under reserve pressure and allowable 
reserve temperature conditions, is always present 
in a gaseous form. 

3.35 Normally Occupied Area — An area where, 
under normal circumstances, humans are present. 

3.36 Normally Unoccupied Area — Area not 
occupied by people but may be occasionally 
entered for brief periods. 

3.37 Nominal Size — A numerical designation of 
size which is common to all components in a piping 
system other than components designated by 
outside diameters or by thread size. It is a conven ient 
round number for reference purposes and is only 

IS 15493 : 2004 

loosely related to manufacturing dimensions. 

3.38 Operating Device — Any component involved 
between actuation and release mechanisms. 

3.39 Prerengineered Systems — Those having 
pre-determined flow rates, nozzle pressures and 
quantities of clean agent. These systems have the 
specific pipe size, maximum and minimum pipe 
lengths, flexible hose specifications, number of 
fittings and number and types of nozzles prescribed 
by a testing laboratory. 

3.40 Primary Release — Release of clean agent 
initiated by detection system or manual operation 
under normal operating conditions. 

3.41 Release — The opening of the cylinder and 
directional valves leading to the physical discharge 
or emission of clean agent into the enclosure. 

3.42 Safety Factor ( SF ) — A multiplier of the 
agent flame extinguishing or inerting 
concentration to determine the agent minimum 
design concentration. 

3.43 Safety Interlock — A switch that monitors the 
occupation of the protected area and automatically 
inhibits the discharge of the clean agent when the 
area is occupied. 

3.44 Sea Level Equivalent of Agent — The agent 
concentration ( volume, percent ) at sea level for 
which the partial pressure of agent matches 
the ambient partial pressure of agent at a given 

3.45 Sea Level Equivalent of Oxygen — The oxygen 
concentration ( volume, percent ) at, sea level for 
which the partial pressure of oxygen matches the 
ambient partial pressure of oxygen at a given 

3.46 Secondary Release ( Slave ) — A release that 
is a consequence and dependent on the operation 
of the primary release, for example, pneumatic 

3.47 Super-presswrization — The addition of a gas 
to the clean agent container, where necessary, to 
achieve the required pressure for proper system 

3.48 Total Flooding — The act and manner of 
discharging an agent for the purpose of achieving a 
specified minimum agent concentration throughout 
a hazard volume. 

3.49 Total Flooding Systems — A fire fighting system 
that is arranged to discharge clean agent into an 
enclosed space to achieve the appropriate design 


4.1 General 

4.1.1 Extinguishing gases are three-dimensional 
agents that are used effectively to suppress fire 
through physical or chemical action. Separate 
properties of specific gases are provided in other 
parts of this standard. 

4.1.2 Gaseous total flooding systems may be used 
to suppress fires of Classes A and B type as defined 
in 3.6 and 3.7. However, for suppressing fires where 
flammable gases may be present, the possibility of 
explosion, during and after system discharge should 
be considered. 

4.1.3 Clean agent gas extinguishing systems are 
useful within the limits, of this standard in 
extinguishing fires in specific hazards or equipment 
and in occupancies where an electrically non- 
conductive medium is essential or desirable, or where 
clean-up of other media poses a problem. 

4.1.4 Where clean agent gas extinguishing systems 
are used, a fixed enclosure shall be provided about 
the hazard that is adequate to enable the specific 
concentration to be achieved and maintained for the 
specified period of time. 

4.1.5 The effects of agent decomposition on lire 
protection effectiveness shall be considered when 
using clean agents in hazards with high temperatures 
( for example, furnaces and ovens, etc ). 

4.1.6 The design, installation, service and 
maintenance of the gas extinguishing systems 
shall be performed by those competent in the 
respective field in accordance with IS 1 5496 : 2004. 

4.1.7 The installer of the clean agent system shall 
be certified by a reputed national/international 
agency/laboratory and such certification shall be 
valid at the time of installation. 

4.2 Suitability md Application 

4.2.1 Total Flooding Systems 

Gaseous fire extinguishing systems are used 
primarily to protect hazards that are in enclosures or 
equipment that, in itself includes an enclosure to 
contain the agent for establishment of required 
concentration and maintenance thereof for the 
required period. Some typical hazards that may 
be suitable include, but or not limited to, the 

a) Within enclosures, such as rooms, vaults, 
enclosed machines, containers, storage tanks 
and bins; 

IS 15493 : 2004 





For enclosed electrical hazards, such as 
transformers, control cubicles, switch boards, 
circuit breakers, and rotating equipment; 

For enclosed flammable liquid/gas storage 
and processing areas; 

For engines using flammable fuels; 
For electronic hazards, such as computers, 
data processing equipment, control room, 
telecommunication facilities; 

Sub-floors and other concealed spaces; and 
Other hieh value assets. 

4.2.2 Some of the gaseous fire extinguishing 
systems may also be used for explosion prevention 
and suppression where flammable materials may 
collect in confined area. 

4.3 Limitations 

4.3.1 Gaseous fire extinguishing systems shall 
not be used on fires involving the following materials 
unless they are pre-evaluated for the purpose: 

a) Certain chemicals or mixture of chemicals, 
such as cellulose nitrate, gun powder, which 
are capable of rapid oxidation in the absence 
of air; 

b) Reactive metals, such as lithium, sodium, 
potassium, magnesium, titanium, zirconium, 
and plutonium; 

c) Metal hydrides or metal amides, some of which 
may react violently with some gaseous 


d) Chemicals capable of undergoing auto- 
thermal decomposition, such as certain 
organic peroxides and hydrazine or; 

e) Mixtures containing oxidizing materials, such 
as sodium chlorate or sodium nitrate; and 

Environments where significant surface 
areas exist at temperatures greater than 
the breakdown temperature of the 
extinguishing agent and are heated by 

Table 1 Halocarbon Agents 

(Clause 4.5.2) 

means other than the fire. 

4,3.2 Electrostatic charging of non-grounded 
conductors may occur during the discharge of 
gaseous fire extinguishing systems. These 
conductors may discharge to other objects causing 
an electric arc of sufficient charge to initiate explosion 
in potentially explosive atmospheres. 

4.4 Other Information 

4.4.1 All devices in respect of the gaseous fire 
extinguishing systems shall be designed for the 
service they will encounter and shall not be readily 
rendered inoperative or susceptible to accidental 
operation. "Normally, the system components shall be 
designed to function properly from -21° to 55°C 
or marked to indicate temperature limitations in 
accordance with the specifications. 

4.4.2 Gaseous fire extinguishing systems may be 
employed to protect more than one enclosure, if 
necessary, by means of directional valves. Where 
there are two or more enclosures simultaneously 
involved in a fire by reason of their proximity, such 
enclosures shall be protected by individual 
systems designed to allow simultaneous operation, 
or a single system sized and arranged to discharge 
on all potentially involved hazards simultaneously. 

4.4.3 Systems employing simultaneous discharge 
of different agents to protect the same enclosure 
shall not be permitted. 

4.5 Applicability of Clean Agents 

4.5.1 The fire extinguishing clean agents addressed 
in the standard are electrically non-conducting and 
leave no residue upon evaporation. 

4.5.2 Tables I and 1A show the details of clean 
agents that are covered in this standard. While 
requirements that are common to all these agents 
are prescribed in this standard, individual 
requirements for each agent are covered under 
separate standards. 

1 No. 

Clean Agent 

Chemical Name 






Dichlorotrifluoroethane ( HCFCM23, 


4.75 percent ) 


Chlorodifloromethane ( HCFC-22. 

( Detox ifier ) 

82 percent) 

Chlorotetranuoroethane ( HCFC-124, 

9.5 percent ) 

Isopropony 1- 1 -methylcyclohexane 

( 3.75 percent ) 








IS 15493 : 2004 

Table 1 A Inert Gas Agents 

(Clause 4.5.2) 

I No. 


an Agent 








N 2 





Chemical Name 


Argon ( 1 00 percent ) 

Nitrogen ( 100 percent ) 

Nitrogen ( 50 percent ) 
Argon ( 50 percent ) 

Nitrogen ( 52 percent ) 
Argon ( 40 percent ) 
Carbon dioxide ( 8 percent ) 




IG 100 


IG 541 

4.5.3 As such, both these standards, that is, for 
genera] and individual requirements should be read 
together before designing a system. Where 
requirements in both the standards differ, standard 
covering individual requirements shall take 


Plans shall contain sufficient details to enable an 
evaluation of the protected enclosure(s) or local 
protection(s) vis-a-vis the effectiveness of the 
system. Details shall include the property involved 
in the hazard(s), location(s), the enclosure limits 
and isolation of the hazards and the exposure of the 

5.1 Plans for submission to the authorities shall 
be drawn up in accordance with the following 








Plans for integrity of fittings shall be clear, 
contain all required details including 
scale and point of compass and shall be clearly 

Name of the enterprise, location and 
detailed postal address; 

Location and construction of the protected 
enclosures, walls and partitions; 

Cross and longitudinal sectional elevations 
of the protection enclosures showing the 
full height, schematic diagram, ceilings, false 
floors, etc; 

Type of clean agent proposed to be used; 

Concentration summary, that is, design, 
extinguishing, injected and inerting, etc; 

Type of the hazards proposed to be 
protected including descriptions of the 
occupancies, surroundings, wall/ceiling 
openings, etc; 

Location of the <*as containers and 










details of the contents, such as volume, 
pressure, nominal capacity in agent mass at 
standard conditions of temperatures and 

Descriptions of pipes and fittings 
indicating also their specifications, pressure 

ratings, etc; 

Descriptions of nozzles employed 
indicating their size, orifice area, type, 
angle, etc, and their locations; 

Electrical cabling and terminations; 

Descriptions of detectors employed 
indicating their locations, mounting, etc; 

Bill of material and equipment schedule for 
each component proposed for the system. 
Suppliers/manufacturers names, details of 
approvals, quantity, etc; 

Isometric drawings showing the agent 
distribution system indicating the lengths 
and diameters, of each pipe segment, nodal 
reference, fittings including unions, reducers, 
orifices, strainers, nozzles, flow rates in all 
segments, equivalent orifice areas, etc; 

Plan view of the enclosures showing the 
entire agent piping system along with 
ceiling, floors, false floors, walls, partitions, 
pipe supports, agent containers, cabling, 
panels, detectors, etc; 

Details showing the pipe supports, agent 
container securement, etc; 

Location of ducts and similar devices, 
dampers, air handling systems, venting 
arrangements and their details with 
supporting calculations, etc; 

Schematic display of the operation of the 
system giving chronological sequence of 
operations prior to the discharge of the agent 
into the protected enclosures; 

Schematic diagrams showing the location 

IS 15493 ; 2004 

and layout of all the power and indicating 
equipment connections, control panels, 
annunciate panels, etc; 

w) Tables showing the calculations for enclosure 
volumes, agent quantity, methods used to 
determine number and location of audible 
and visual indicating equipment, number and 
location of detectors, etc; and 

y) Other features like interconnection with 
other type of fire protection systems, etc, with 
the proposed system. 

5.2 The details of the system shall include 
information and calculations on the amount of agent; 
container storage pressure; internal volume of the 
containers; the location, type and flow rate of each 
nozzle including equivalent orifice area; the location, 
size and equivalent lengths of pipe, fittings, siphon 
tube, valve, discharge head and flexible connector 
hose; and the location and size of the storage facility. 
Pipe size reductions and orientation of tees shall be 
clearly indicated. Details shall be available on location 
and function of the detection devices, operating 
devices, auxiliary equipment and electrical circuitry. 
All the apparatus, equipment used in the system shall 
be easily identifiable. 

5.3 An as-built drawing shall be submitted upon 
completion of the installation for approval. Instruction 
and maintenance manuals that include a full 
sequence of operations and a full set of drawings and 
calculations shall be available on site. 

5.4 Flow Calculations 

System flow calculations along with the working 
drawings shall be submitted to the authorities in 
advance for approval. The hydraulic calculations 
shall be performed using calculation method approved 
by the authorities. 


6.1 Safety Precautions ( for Personnel ) 

The discharge of some of the gas agents in fire 
extinguishing concentrations creates serious hazards 
for personnel in both the protected area and the areas 
to which the gas may migrate and also to properties 
in the vicinity of agent discharge. These hazards may 
include reduced visibility, suffocation and toxicity, 
during and after the discharge period. The relevant 
information on the above is available in Annex B. 

The toxicity information on the gaseous fire agents 
■is given in Table 2. More details are specified in 
other relevant standard. Where hazardous 
concentrations of agent may exist, lock-off valves shall 
be fitted to the system. 

In areas, where there is a likelihood of significant 
difference between gross and net volumes of the 
enclosure, utmost care shall be exercised in proper 
system design to ensure that maximum concentrations 
are not exceeded. 

6.1.1 Safety Precautions (for Protected Areas ) 

a) Normally occupied area — The minimum 
safety precautions taken shall be in 
accordance with Table 2A and provisions 
therein, and 

b) Normally unoccupied areas — The maximum 
concentration shall not exceed the LOAEL 

for the agent used unless a lock-off valve is 

Warning — Any change to the enclosure 
volume, or addition or removal of contents 
that was not covered in the original design 
will affect the concentration of agent. In such 
instances the system shall be re-calculated 
to ensure that the required design 
concentration is achieved and that the NOAEL 
or the LOAEL are not exceeded. 

6.1.2 For unoccupiable areas, the maximum 
concentration may exceed the LOAEL for the 
extinguishant used, without the need for a lock- 
off valve to be fitted. 

6.1.3 Protection of Occupants 

In any use of the gaseous system, where there is a 
possibility that people may enter or have difficulty 
seeking egress from the protected enclosure, suitable 
safeguards shall be provided. Such safety aspects 
as personal training, warning signs, pre-discharge 
alarms and safety interlocks shall be provided. Means 
of proper ventilation after fire should be readily 

6.2 Safety Precautions ( Total Flooding Systems ) 

6,2.1 In areas protected by total flooding systems, 
that are capable of being occupied, the provision of 
the following safety aspects shall apply: 

a) Mandatory requirements: 

1) A time delay shall be provided for 
evacuation prior to agent discharge. 
The agent discharge delay time shall be 
based on an engineering assessment of 
egress time for occupants in the area 

2) Safety interlocks and lock-off valves 
shall be provided wherever required 
as per Table 2. 

IS 15493 : 2004 

Table 2 Toxicity Information on Clean Agent Suppression Systems 

( Clauses 6.1 and 6.2 A ) 

SI No. 

Clean Agent 

Chemical Formula 

( Percentage by Vol 

ume ) 









Blend A 

CHCI2CF3 ( 4.75 percent ) 
CHC1F2( 82 percent) 
CHCIFCF3 ( 9.5 percent ) 
Detoxifier (3.75 percent) 












Nitrogen ( 52 percent ) 
Argon ( 40 percent ) 
Carbon dioxide ( 8 percent ) 






Nitrogen ( 50 percent ) 
Argon ( 50 percent ) 






Nitrogen ( 100 percent ) 







Argon ( 100 percent ) 




Table 2A Minimum SafetyPrecautions 

( Clauses 6.1.1 and^.lA ) 

1 No. 

Injected Agent 





Up to NOAEL 


Above NOAEL and 

up to LOAEL 


Above LOAEL 




Svvitcli and 
Time Delay 

in 30 s 










Not required 

Not required 




Not required 


Not Applicable !) Required 


NOTE — Thepurpose of the table is to avoid unnecessary exposure of occupants to the agent discharged. Factors such 
as the time for egress and the risk to the occupants by the fire must be considered when determining the system discharge 
time delay. 

^Concentration levels above LOAEL arenot permitted in occupied areas and question of egress does not arise. 

3) Exit routes which shall be kept clear at 
all times and the provision of 
emergency lighting and adequate 
direction signs to minimize travel 

4) Outward swinging self-closing doors 
which can be opened from inside 
including when locked from the outside, 

5) Continuous visual and audible alarms 
at entrances and designated exits until 
the protected area has been made safe, 

6) Warning and instruction signs shall be 
arranged as per clause, 

7) Pre-discharge alarms within such areas 
that are distinctive from all other alarm 
signals and that will operate immediately 
upon detection of fire, 

8) Means of prompt ventilation of such areas 
after any discharge of agent. Forced draft 
ventilation will often be necessary. Care 
shall be taken to completely dissipate 
hazardous atmospheres and not just 
move them to other locations, as agents 
are generally heavier than air, and 

9) Instructions and drills of all personnel 
within or in the vicinity of protected 
areas, including maintenance and 
construction personnel who may be 
brought into the area, to ensure their 
correct actions when the system operates. 

b) Recommendatory requirements: 

1) Adding an odour to the agent so that 
the hazardous atmospheres are 

IS 15493: 2004 

2) Self-contained breathing apparatus 
and personnel trained for its use, and 

3) Means to detect a hazardous 
atmosphere in or around the protected 

6,2.2 Electrostatic Discharge 

To avoid a situation as stated in 4.3.2, the components 
of the inerting system, such as pipe work, etc, shall 
be bonded and earthed as per National Electrical 
Code (SP 30: 1985). 

6.3 Miscellaneous Hazards 

Certain other types of hazards associated with the 
usage of gaseous systems are as under: 

a) Noise — Discharge of a gaseous system can 
cause a noise loud enough to be startling, 
but not enough to cause traumatic injury; 

b) Turbulence — The turbulence caused by the 
high velocity discharge from nozzles may be 
sufficient to dislodge substantial objects 
directly in its path, such as ceiling tiles and 
light fittings. Therefore, tiles and light fittings 
should be properly anchored. System 
discharge may also cause enough general 
turbulence in the enclosure to move unsecured 
paper and light objects; 

c) Electrical clearance — Where exposed 
electrical conductors are present, all system 
components shall be located no less than 
the minimum clearances from the energized 
parts. The clearances stipulated in National 
Electrical Code shall be maintained for safe 
operating conditions. Where the design basic 
insulation level is not available and where 
nominal voltage is used for the design criteria 
the highest minimum clearance listed for the 
purpose shall be used; and 

d) Other hazards, if any, appropriate to the 
selected gaseous agent as specified in the 
other clauses of this standard shall be given 
due attention. 


7,1 Unclosable Openings 

a) The protected enclosure shall have sufficient 
structural strength and integrity to contain 
the agent discharge; 

b) The area of the unclosable openings such 
as ventilator openings within the enclosure 
shall be kept to as least as possible to avoid 
ingress of the agent through the leakages 
to the adjoining areas. Where confinement 
of the agent within the enclosure is not 

practicable, protection shall be extended 
to include the adjacent connected hazards 
or work areas; 

c) Particular attention should be given to 
openings around cable, duct and pipelines 
( similar utility services ) penetrating 
through the wall(s) and floor(s); 

d) In case of unavoidable openings, such 
openings should be restricted to as minimum 
as possible; 

e) In such cases, quantity of agent need to be 
suitably increased in consultation with the 
authorities concerned for maintaining the 
desired concentration within the 

In case of item (c) above, the openings 
should be effectively sealed or preferably 
fire studded; and 

g) Injecting more quantity of agent in most of 
the cases, will only increase the rate of loss 
of agent through such openings. Hence, 
openings in the wall(s) and floor(s) shall be 
kept only to optimum requirements with 
increase in quantity of agent as discussed 
in item (d) above. 

7.2 Air Handling System and Similar Services 

a) Humidification and air handling systems 
catering to the protected areas shall be 
capable of automatic shutdown prior to the 
agent discharge. Also dampers shall be 
available inside the systems to stop flow 
of agent through ducts and similar means 
and these shall close automatically prior to 
agent discharge; 

b) Where it is necessary for air handling 
systems to be kept operating to provide 
cooling arrangement for essential equipment, 
quantity of the agent shall need to be 
suitably increased to include the volumes of 
both air and the ventilation system in 
addition to the volume of protected 
enclosure in consultation with the authorities 
concerned for maintaining the desired 
concentration within the enclosure; 

c) The operations within the enclosure that 
are likely to disperse the discharge of the 
agent, such as pumps, spray guns, heaters, 
etc, shall not be left running during the 
discharge of the agent and suitable provisions 
shall be available to shut them down prior 
to agent discharge; and 

d) In case of extinguishment of deep-seated 
fires such as those involving solids. 
Unclosable openings shall be provided 

IS 15493: 2004 

only in the ceiling level and such openings 
near the walls and partitions shall be 



8.1 Agent Supply and Container Arrangement 
8.1.1 Agent Supply 

a) Quality Requirement — The clean agent 
shall comply with quality and purity 
standards appropriate to the agent selected 
for extinguishment. Each batch of agent 
manufactured shall be tested and certified 
to applicable specification. Agent blends 
shall remain homogeneous in storage and 
use within the approved temperature 
range and environmental conditions at the 
place of installation; 

b) Quantity Requirements ( Main ) — The 
amount of agent in the system shall be at 
least sufficient for the largest single 
hazard or group of hazards to be protected 

c) Quantity Requirements (Reserve) — Same 
quantity equivalent to the largest single 
hazard or group of hazards to be protected 
simultaneously shall be available as 
reserve. However, if the replenishing of 
agent supply takes more than 7 days at the 
site of installation, authority concerned 
may insist on more quantity to be kept 
available as reserve; and 

d) Uninterrupted Protection — Where 
uninterrupted protection is required, both 
the main and reserve supply shall be 
permanently connected to the distribution 
piping and arranged for easy change-over. 

8.1.2 Agent Storage 

a) Agent shall be stored in containers designed 
to hold that specific agent at ambient 

b) Agent containers shall be charged to a fill 
density or super-pressurization level with 
range specified by the manufacturers, 

c) Agent storage temperatures shall not 
exceed 55°C or be less than -2 1 °C. External 
heating or cooling shall be employed to 
keep the temperature of the agent storage 
container within the above limits if situation 
warrants so, 

d) The agent containers used in the flooding 
systems shall be designed to meet the 
requirements of the Department of 

Explosives, Nagpur, 

e) Each agent container shall have ;a 
permanent nameplate or other permanent 
marking that indicate the details as 
per Table 4. 

f) A reliable means shall be provided to 
determine the pressure in refillable super- 
pressurized containers, and 

g) Th£ agent containers connected to a 
common manifold shall conform as per the 
provisions in Table 5. 

Table 4 Marking on Storage Container 

[Clause 8.1.2(e)] 

SI No. 

Clean Agent 

Marking on Container 





Halocarbon clean 

Name of the agent 
Tare and agents gross weights 
Super-pressurization level of 
the container 


Inert gas clean 

Name of the agent 


Pressurization level of the 


Nominal agent volume 

Table 5 Arrangement of Containers with 
Common Manifold 

[Clause 8. 1.2(g)] 

Si No. Clean Agent 

(1) (2) 

i) Halocarbon clean 

ii) Inert gas clean 

Containers with 
Common Manifold 


Agents in a multiple 
container system — all 
containers supplying the 
same manifold outlet for 
distribution of the same 
agent shall be 

interchangeable, of same 
nominal size and capacity, 
filled with same nominal 
mass of agent and 
pressurized to the same 
nominal working pressure 

Agents shall be permitted to 
utilize multiple storage 
container sizes connected 
to the common manifold 
provided the containers are 
all pressurized to the same 
nominal working pressure 

8 J. 3 Storage Container Arrangement 

The arrangement of storage containers and 
accessories shall be as follows: 

a) Containers and accessories shall be located 
and arranged so that inspection testing, 

IS 15493:2004 

recharging and other maintenance is 
facilitated, and interruption to protection is 
kept to a minimum; 

b) Containers should be located outside and 
as near as practical to the enclosure 
protected. Containers protecting a single 
risk can be located within the enclosure 
they serve, only if sited so as to minimize 
the risk of exposure to fire and explosion; 

c) Containers shall be located so as not to be 
subject to severe weather conditions or to 
mechanical, chemical or other damage. 
Where excessive climatic or mechanical 
exposures are expected, suitable guards or 
enclosures shall be provided; 

d) Containers shall be adequately mounted 
to allow free passage of air around the base 
and suitably supported to provide for 
convenient individual servicing or content 
weighing. There shall be enough space 
for a full on-site inspection of the base of 
the container; 

e) In manifold systems, non-return valves 
or other automatic means shall be provided 
to prevent a loss of agent and to ensure 
personnel safety if the system is operated 
when any containers are removed for 

f) Containers brackets or devices integral 
with the container for attachment to 
structures shall be designed to cater for the 
maximum expected mass, vibration effects 
and shock loading, appropriate to the 

g) Reserve containers, where provided, shall 
be permanently sited or arranged for easy 
changeover; and 

h) Storage containers are located in areas 
where their leakage could lead to a 
hazardous concentration, consideration 
shall be given to the installation of gas 
detectors or other means to provide 
warning on the onset of hazardous 

8.2 Agent Distribution Arrangements 

8,2.1 General 

a) Pipe network, fitting shall be of non- 
combustible construction having physical 
and chemical properties such that their 
integrity under stress can be predicted with 

b) In severely corrosive atmospheres, special 

corrosion resistant materials shall be 
required for pipes, fittings or support 
brackets and steelwork; 

c) Before final assembly, pipes and fittings 
shall be inspected visually to ensure they 
are free of burrs, swelter and rust and that 
no foreign matter is inside and the full bore 
is clear. After assembly, the system shall be 
thoroughly blown through with dry air or 
compressed gas. The pipe work shall be free 
of particulate matter and oil residue before 
the installation of nozzles and discharge 

d) A dirt trap consisting of a 'tee 1 with a capped 
nipple at least 50 mm long should be 
installed at the end of each pipe run. Drain 
traps should also be necessary if there is a 
possibility of a build-up of water; 

e) In systems where valve arrangements 
introduce sections of closed piping, such 
sections shall be equipped with the 

1) Indication of agent trapped in piping; 

2) Means for safe manual venting; and 

3) Automatic relief of excess pressure, 
where required, 

f) Pressure relief devices, which can include 
the selector valve, shall be fitted so that 
the discharge, in the event of operation, will 
not endanger the personnel; and 

g) In systems using pressure-operated 
container valves, automatic means shall be 
provided to vent any container leakage that 
could build up pressure in the pilot system 
and cause unwanted opening of the container 
valve. The means provided for pressure 
venting shall not prevent operation of the 
container valve. 

8,2.2 Piping Network 

8.2.2*1 The piping used in the installation shall 
conform to the following requirements: 

a) Cast iron or non-metallic pipes shall not be 
used anywhere; 

b) Where used, flexible pipes, tubing, or hoses 
including connections shall be of approved 
materials with adequate temperature and 
pressure ratings; and 

c) The thickness of the pipes shall be in 
accordance with the provisions laid down 
in IS 6631. The internal pressure used for 
this calculation shall not be less than the 
greater of either of the following values: 


1) The normal charging pressure in the 
agent container at 2 1 °C. 

2) 80 percent of the maximum pressure in 
the agent container at the maximum 
storage temperature of not less than 
55°C using the maximum allowable fill 
density specified by the manufacturer, 
if applicable. 

d) Pipe joints shall be either threaded, welded 
or flanged type only and other types of 
jointing shall not be allowed. 

In no case shall the value used, for the minimum 
piping design pressure, be less than that specified in 
Tables 6 and 7 for the conditions shown. 

For halocarbon agents Table 6 shall be used and for 
inert gas agents Table 7 shall be used. 

Where different fill densities, pressurization levels 
or higher storage temperatures other than the 

IS 15493: 2004 

values shown in the tables are used with prior 
acceptance of the authorities, the minimum design 
pressure for the piping shall be adjusted to the 
maximum pressure in the agent container at 
maximum temperature, using the basic design 
criteria specified in items c( 1 ) and c(2) above. 

8.2,3 Pipe Fittings 

a) The sizes and dimensions of pipe fittings 
shall be in accordance with IS 1239 ( Part 2 ). 
Fittings shall be capable to withstand 
minimum rated working pressure equal to or 
greater than the minimum working 
pressure specified in (c) for the clean 
agent being used. For systems that use a 
pressure reducing device in the distribution 
piping, the fittings downstream the device 
shall have a minimum rated working 
pressure equal to or greater than the 
maximum anticipated pressure in the 
downstream piping; 

Table 6 Minimum Design Working Pressure for Halocarbon Clean Agent System Piping 

(Clause 8.2,2.1) 

SI No. 

Clean Agent 


nt Container 

Agent Container 

Agent Container 


Maximum Fill 



Piping Design 





kg/m 2 

at 21°C 

at 55°C 

at 21°C 











1 034 1 * 

1 703 

1 365 

1 152 

2 482'> 

3 585 

2 868 

1 120 

4 137 l > 

4 950 

3 958 




4 137 l > 

5 860 

4 689 


2 482»> 

3 723 

2 979 


jper-pressurized with 


Table 7 Minimum Design Working Pressure for Inert Gas Clean Agent System Piping 

(Clause 8.2. 2.1) 

SI No. 

Clean Agent 

Agent Container 

Charging Pressure 

at 21°C 


Agent Container 
Charging Pressure 

at 55°C 

Minimum Design Pressure at 21°C 


Piping Upstream 

of Pressure 



of Pressure 










16 341 

20 424 

18 271 

22 778 

16 341 

14 997 

6 723 
6 728 



14 997 
19 996 

17 755 
23 671 

14 997 
19 996 

6 895 
6 895 



15 521 
20 424 
30 636 

17 065 
22 753 
34 130 

15 318 
20 424 
30 633 

6 550 
6 550 
6 550 



16 580 
22 311 

19 300 
26 014 

16 580 
22 311 

6 895 
6 895 


IS 15493 : 2004 

b) Cast iron fittings shall not be used All 
threads used in joints and fittings shall 
comply with relevant Indian Standards; 

c) Welding of joints shall comply with relevant 
Indian Standards; and. 

d) Where copper, stainless steel, or other 
suitable tubing is jointed with compression 
type fittings, manufacturers pressure and 
temperature ratings of the fittings shall 
not be exceeded. 

8.2.4 Pipe Installation and Supports 

a) In the installation of pipe work, care shall be 
taken to avoid possible restrictions due to 
foreign matter, faulty fabrication or improper 
installation. Pipe ends shall be reamed after 
cutting, where required; 

b) Where there is a possibility of explosions, 
the piping shall be attached to supports that 
are least likely to be displaced; and 

c) The maximum distance between supports shall 
take into account the total mass of pipe and 
the agent used. Distance between supports 
is indicated in Table 8. 

Table 8 Maximum Pipe Work Distances 

[Clause 8.2.4(c)] 

SI No. Nominal Diameter 
















of Pipe 

















Maximum Pipe 
Work Distance 






8.2.5 Discharge Nozzles 

a) Nozzles, including nozzles directly 
attached to containers, shall be of approved 
type and located with the geometry of the 
enclosure under consideration. 

b) The type, number and placement of 

nozzles shall be such that; 

1) The design concentration shall be 
achieved in all parts of the enclosure; 

2) The discharge shall not unduly splash 
flammable liquids or create dust clouds 
that might extend the fire, create an 
explosion or otherwise adversely affect 
the occupants; 

3) The velocity of discharge shall not 
adversely affect the enclosure or its 

4) The discharge nozzles shall be provided 
with frangible discs or blow-out caps 
where clogging by foreign materials is 
possible. These devices shall provide 
an unobstructed opening upon system 
operation and shall be arranged so they 
will not injure personnel; 

5) Nozzle shall be suitable for the 
intended use and shall be approved for 
discharge characteristics. The discharge 
nozzle consists of the orifice and any 
associated horn, shield or baffle; 

6) Nozzles shall be of adequate strength 
for use with the expected working 
pressures, be able to resist nominal 
mechanical abuse, and be constructed 
to withstand expected temperatures 
without deformation; and 

7) Nozzle discharge orifice inserts shall 
be of corrosion-resistant material. 

c) In order to minimize the possibility of 
lifting or displacement of lightweight 
ceiling tiles, precautions shall be taken to 
securely anchor the tiles for a minimum 
distance of 1 .5 m from each discharge nozzle. 



9.1 General 

9.1.1 Detection, actuation, alarm and control 
systems shall be installed, tested and maintained 
in accordance with IS 2 1 89. 

9.1.2 Automatic detection and automatic actuation 
shall be used. 

9.2 Automatic Detection 

9.2J Automatic detection shall be by any 
approved method or device capable of detecting 
and indicating heat, flame, smoke, combustible 
vapours or any abnormal condition in the hazard, 
such as process trouble, that is likely to produce 


IS 15493 : 2004 

9.2.2 Adequate and reliable primary and 24 h 
minimum standby sources of energy shall be used to 
provide for operation of the detection, signalling, 
control and actuation requirements of the system. 

9.2.3 When a new agent system is being installed 
in a space that has an existing detection system, an 
analysis shall be made of the detection devices to 
assure that the detection system is in good 
operating condition and will respond promptly to a 
fire situation. This analysis shall be done to assist 
in limiting the decomposition products from a 
suppression event. 

9.3 Operating Devices 

9.3.1 Operating devices shall include agent 
releasing devices or valves, discharge controls and 
shutdown equipment necessary for successful 
performance of the system. 

9.3.2 Operation shall be by approved mechanical, 
electrical or pneumatic means, adequate and reliable 
source of energy shall be used. 

9.3.3 All devices shall be designed for the 
service they will encounter and shall not readily be 
rendered inoperative or susceptible to accidental 
operation. Devices normally shall be designed to 
function properly from -20° to 55°C or marked to 
indicate temperature limitations. 

NOTE — Also care shall be taken to thoroughly 
evaluate and correct any factors that could result in 
unwanted discharge. 

9.3.4 All devices shall be located, installed or suitably 
protected so that they are not subject to mechanical, 
chemical or other damage that would render them 

9.3.5 A mean of manual release of the system 
shall be provided. Manual release shall be 
accomplished by a mechanical manual release or 
by an electrical manual release when the control 
equipment monitors the battery voltage level of the 
standby battery supply and will provide a low 
battery signal. The release shall cause 
simultaneous operation of automatically operated 
valves controlling agent release and distribution. 

9.3.6 The normal manual control(s) for actuation 
shall be located for easy accessibility at all times, 
including at the time of a fire. The manual control(s) 
shall be of distinct appearance and clearly recognizable 
for the purpose intended. Operation of any control 
shall cause the complete system to operate in its normal 

9.3.7 Manual controls shall not require a pull of 
more than 18.1 kg ( 178 N ) nor a movement of more 
than 355 mm to secure operation. At least one manual 

control for activation shall be located not more than 
1 2 m above the floor. 

9.3.8 Where gas pressure from the system or pilot 
containers is used as a means for releasing the 
remaining containers, the supply and discharge 
rate shall be designed for releasing all of the 
remaining containers. 

9.3.9 All devices for shutting down supplementary 
equipment shall be considered integral part of the 
system and shall function with the system 

9.3.10 All manual operating devices shall be 
identified as to the hazard they protect. 

9.4 Control Equipment 

9.4.1 Electric Control Equipment 

The control equipment shall supervise the 
actuating devices and associated wiring and, as 
required, cause actuation. The control equipment 
shall be specifically listed for the number and type 
of actuating devices utilized and their compatibility 
shall have been approved. 

9.4.2 Pneumatic Control Equipment 

Where pneumatic control equipment is used, the 
lines shall be protected against crimping and 
mechanical damage. Where installations could be 
exposed to conditions that could lead to loss of 
integrity of the pneumatic lines, special precautions 
shall be taken to ensure that no loss of integrity will 
occur. The control equipment shall be specifically 
listed for the number and type of actuating devices 
utilized and their compatibility shall have been 

9.5 Operating Alarms and Indicators 

9.5.1 Alarms or indicators or both shall be used to 
indicate the operation of the system, hazards to 
personnel, or failure of any supervised device. The 
type ( audible, visual or olfactory ), number, and 
location of the devices shall be such that their 
purpose is satisfactorily accomplished. The extent 
and type of alarms or indicator equipment or both 
shall be approved. 

9.5.2 Audible and visual pre-discharge alarms shall 
be provided within the protected area to give positive 
warning of impending discharge. The operation of 
the warning devices shall be continued after agent 
discharge until positive action has been taken to 
acknowledge the alarm and proceed with appropriate 

9.5.3 Abort switches generally are not 
recommended, however, where provided, the abort 


IS 15493: 2004 

switches shall be located within the protected area 
and shall be located near the means of egress from 
the area. An abort switch shall not be operated 
unless the cause for the condition is known and 
corrective action can be taken. The abort switch 
shall be of a type that requires constant manual 
pressure to cause abort. The abort switch shall not 
be of a type that would allow the system to be left in 
an aborted mode without someone present. In all 
cases the normal and manual emergency control 
shall override the abort function. Operation of the 
abort function shall result in both audible and distinct 
visual indication of system impairment. The abort 
switch shall be clearly recognizable for the purpose 

9.5.4 Alarms indicating failure of supervised 
devices or equipment shall give prompt and positive 
indication of any failure and shall be distinctive 
from alarms indicating operation or hazardous 

9.5.5 Warning and instruction signs at entrances to 
and inside protected areas shall be provided. 

9.5.6 Indication lamps shall be provided to indicate 
the status of the abort switch, that is, Green colour 
for 'Auto', Yellow colour for the 'Manual' and Red 
colour for 'Discharge' modes. 

9.6 Time Delays 

9.6.1 For clean agent extinguishing systems, a 
pre-discharge alarm and time delay, sufficient to 
allow personnel evacuation prior to discharge, shall 
be provided. For hazard areas subject to fast 
growth Fires, where the provision of a time delay 
would seriously increase the threat to life and 
property, a time delay shall be permitted to be 

9.6.2 Time delays shall be used only for personnel 
evacuation or to prepare the hazard area for 

9.6.3 Time delays shall not be used as a means of 
confirming operation of a detection device before 
automatic actuation occurs. 


The minimum requirements for the commissioning and 
acceptance of the gaseous extinguishing system shall 
be as follows. 

10.1 General 

The completed system shall be reviewed and tested 
by a competent person to meet the approval of the 
authority. Only equipment and devices designed 
to national standards shall be used in the systems. 

To determine that the system has been properly 
installed and will function as specified, the tests 
specified in 10,2.2 to 10.2.9 shall be performed. 

10,2 Review of Mechanical Components 

10.2.1 The piping distribution system shall be 
inspected to determine that it is in compliance with 
the design and installation documents. 

10.2.2 Nozzles and pipe size and, if appropriate, 
pressure- reducing devices, shall be in accordance with 
system drawings. The means for pipe size reduction 
and attitudes of tees shall be checked for conformance 
to the design. 

10.2.3 Piping joints, discharge nozzles and piping 
supports shall be securely fastened to prevent 
unacceptable vertical or lateral movement during 
discharge. Discharge nozzles shall be installed in such 
a manner that piping cannot become detached 
during discharge. 

10.2.4 During assembly, the piping distribution 
system shall be inspected internally to detect the 
possibility of any oil or particulate matter which 
could soil the hazard area or affect the agent 
distribution due to a reduction in the effective 
nozzle orifice area. 

10.2.5 The discharge nozzles shall be oriented in 
such a manner that optimum agent dispersal can be 

10.2.6 If nozzle deflectors are installed, they shall 
be positioned to obtain the maximum benefit. 

10.2.7 The discharge nozzles, piping and mounting 
brackets shall be installed in such a manner that they 
will not potentially cause injury to personnel. Agent 
shall not directly impinge on areas where personnel 
may be found in the normal work area, or on any loose 
objects or shelves, cabinet tops, or similar surfaces 
where loose objects could be present and become 

10.2.8 All agent storage containers shall be properly 
located in accordance with 'approved for construction' 
set of system drawings. 

10.2.9 All containers and mounting brackets shall 
be securely fastened in accordance with the 
manufacturer's requirements. 

10.2.10 An adequate quantity of agent to produce 
the desired specified concentration shall be 
provided. The actual enclosure volumes shall be 
checked against those indicated on the system 
drawings to ensure the proper quantity of agent. Fan 
rundown and damper closure time shall be taken into 


IS 15493 : 2004 

10,2.11 Unless the total piping contains not 
more than one change in direction fitting between the 
storage container and the discharge nozzle, and 
unless all piping has been physically checked for 
tightness, the following tests shall be carried out: 

a) All open ended piping shall be pneumatically 
tested in a closed circuit for a period of 10 
min at 3 bar. At the end of 1 min, the pressure 
drop shall not exceed 20 percent of the test 
pressure, and 

b) All closed-section pipe work shall be 
hydrostatically tested to a minimum of 
1 .5 times the maximum working pressure for 
2 min during which there shall be no 
leakage. On completion of the test, the pipe 
work shall b$ purged to remove moisture. 

It is recommended that hydrostatic testing be carried 
out at the manufacturer's works where practicable. 

WARNING — Pneumatic pressure testing creates 
a potential risk of injury to personnel in the area, 
as a result of airborne projectiles if rupture of the 
piping system occurs. Prior to conducting the 
pneumatic pressure test, the protected area shall 
be evacuated and appropriate safeguards shall 
be provided for test personnel. 

10.2.12 A test using nitrogen, or a suitable 
alternative, shall be performed on the piping 
network to verify that flow is continuous and that the 
piping and nozzles are unobstructed. 

10.2.13 Where required, suitable venting facilities 
shall be provided for the release of excessive pressure 
build-up during discharge of the agent. Individual 
standards for gaseous agents provide details for the 
design of venting facilities. 

10.3 Review of Electrical Components 

10.3.1 All wiring systems shall be properly installed 
in compliance with the appropriate National 
Standard and the system drawings, a. c. and d.c. wiring 
shall not be combined in a common conduit unless 
properly shielded and grounded. 

10.3.2 All field circuitry shall be tested for ground 
fault and short circuit condition. When testing field 
circuitry, all electronic components ( such as smoke 
and flame detectors or special electronic equipment 
for other detectors, or their mounting bases ) shall 
be removed and jumpers properly installed to prevent 
the possibility of damage within these devices. Replace 
components after testing the circuits. 

10.3.3 Adequate and reliable primary standby 
sources of energy which comply with 9.2.2 shall be 
used to provide for operation of the detection, 

signalling, control and actuation requirements of the 

10.3.4 All auxiliary functions (such as alarm 
sounding or displaying devices, remote annunciators, 
air handling shutdown, power shutdown, etc ) shall 
be checked for proper operation in accordance with 
system requirements and design specifications. 

Alarm devices shall be installed so that they are 
audible and visible under normal operating and 
environmental conditions. 

Where possible, all air handling and power cut-off 
controls should be of the type that once interrupted 
require manual restart to restore power. 

10.3.5 Check that for systems using alarm silencing, 
this function does not affect other auxiliary functions, 
such as air handling or power cut-off where they are 
required in the design specification, 

10.3.6 Check the detection devices to ensure that 
the types and locations are as specified in the 
system drawings and are in accordance with the 
manufacturer's requirements, 

10.3.7 Check that manual release devices are 
properly installed, and are readily accessible, 
accurately identified and properly protected to 
prevent damage. 

10.3.8 Check that manual release devices used to 
release agents require two separate and distinct 
actions for operation. They shall be properly 
identified. Particular care shall be taken where 
manual release devices for more than one system are 
in close proximity and could be confused or the 
wrong system actuated. Manual release devices in 
this instance shall be clearly identified as to which 
hazard enclosure they protect. 

10.3.9 Check that for systems with a main/reserve 
capability, the main/reserve switch is properly 
installed, readily accessible and clearly identified, 

10.3.10 Check that for systems using inhibit 
switches requiring constant manual force, these are 
properly installed, readily accessible within the 
hazard area and clearly identified. 

10.3.11 Check that the control panel is properly installed 
and readily accessible. 

10.4 Preliminary Functional Tests 

10.4.1 Where a system is connected to a remote 
central alarm station, notify the station that the fire 
system test is to be conducted and that an 
emergency response by the fire department or alarm 
station personnel is not required. Notify all concerned 
personnel at the end-user's facility that a test is to 


IS 15493 : 2004 

be conducted and instruct them as to the sequence 
of operation. 

10.4.2 Disable or remove each agent storage 
container release mechanism and selector valve, 
where fitted, so that activation of the release circuit 
will not release agent. Reconnect the release circuit 
with a functional device in lieu of each agent storage 
container release mechanism. 

For electrically actuated release mechanisms, these 
devices may include suitable lamps, flash bulbs or 
circuit breakers. Pneumatically actuated release 
mechanisms may include pressure gauges. Refer to 
the manufacturer's recommendations in all cases. 

10.4.3 Check each resetable detector for proper 

10.4.4 Check that polarity has been observed on all 
polarized alarm devices and auxiliary relays. 

10.4.5 Check that all required end-or-line devices 
have been installed. 

10*4.6 Check all supervised circuits for correct fault 

10.5 System Functional Operational Test 

10.5.1 Operate the detection initiating circurt(s). 
All alarm functions shall occur according to the 
design specification. 

10.5.2 Operate the necessary circuit to initiate a 
second alarm circuit if present. Verify that all 
second alarm functions occur according to design 

10.5.3 Operate the manual release device. Verify 
that manual release functions occur according to 
design specifications. 

10.5.4 Where appropriate, operate the inhibit 
switch. Verify that functions occur according to the 
design specifications. Confirm that visual and 
audible supervisory signals are.received at the control 

10.5.5 Check the function of all resettable valves 
and activators, unless testing the valve will release 
agent. 'One-shot' valves, such as those incorporating 
frangible discs, should not be tested. 

10.6 Remote Monitoring Operations ( If 
Applicable ) 

10.6.1 Disconnect the primary power supply, then 
operate one of each type of input device while on 
standby power. Verify that an alarm signal is received 
at the remote panel after the device is operated. 
Reconnect the primary power supply. 

10.6,2 Operate each type of alarm condition and 
verify receipt of fault condition at the remote 

10.7 Control Panel Primary Power Source 

10.7.1 Verify that the control panel is connected to a 
dedicated unswitched circuit and is labelled properly. 
This panel shall be readily accessible but access shall 
be restricted to authorized personnel only. 

10.7.2 Test a primary power failure in accordance 
with the manufacturer's specification, with the system 
fully operated on standby power. 

10.8 Review of Enclosure Integrity 

It is preferable to subject all total flooding systems 
to an Enclosure Integrity jfcst in order to detect 
and seal the significant leakage paths that could 
result in failure of an enclosure to withhold design 
concentration for a specified period ( see 7.1 
and 10.10), 

10.9 Completion of Functional Tests 

When all functional tests are complete ( see 10.6 
to 10.9 ), reconnect each storage container so that 
activation of the release circuit will release the agent. 
Return the system to its fully operational design 
condition. Notify the central alarm station and all 
concerned personnel at the end-user's facility that 
the fire system test is complete and that the system 
has been returned to full service condition by following 
the procedures specified in the manufacturers' 

10.10 The complete installation shall be tested in 
one of the two methods narrated below: 

a) Full-scale discharge test, and 

b) Enclosure integrity test. 

Where the authorities concerned insist on 
full-scale discharge test, the test shall be 
conducted in accordance with various provisions 
under Annex C and results of the test ( that is 
concentration achieved, discharge time, holding 
time ) shall conform to various provisions available 
in other clean agent standards with particular 
reference to the agent used. Otherwise, the enclosure 
where total flooding system is installed, shall be 
subject to 'enclosure integrity test 1 in accordance with 
various provisions under Annex D to demonstrate 
the retention time ( of the required concentration 
with the enclosure ) as specified in other standards 
with particular reference to the agent used. 

10.11 Completion Certificate and Documentation 

The installer shall provide to the user a completion 


IS 15493:2004 

certificate, a complete set of instructions, calculations 
and drawings showing the system as-installed, and 
a statement that the system complies with all the 
appropriate requirements of this standard, and giving 
details of any departure from appropriate 
recommendations. The certificate shall give the design 
concentrations and, if carried out, reports of any 
additional test including the door fan test. 


11.1 General 

System flow calculations shall be carried out at a 
nominal agent storage temperature of 21°C, shall 
have been validated by an accredited approval 
authority by appropriate tests as described in this 
standard, and shall be properly identified. The 
system design shall be within the manufacturer's 
specified limitations. 


1 Variations from the nominal 21°C storage 
temperature will affect flow conditions used in 

2 Pre-engineered systems do not require a flow 
calculation when used within approved 

11.2 Balanced and Unbalanced System 

-11.2.1 A balanced system shall be one in which: 

a) each actual or equivalent pipe length from 
the container to each nozzle are all within 1 
percent of each other, and 

b) the discharge rate of each nozzle is equal. 

11.2.2 Any system that does not meet the criteria 
mentioned in 11.2 shall be considered to be an 

unbalanced system. 

1 1.3 Friction Losses 

Allowance shall be made for the friction 
tosses in pipes and in container valves, dip tubes, 
flexible connectors, selector valves, time delay 
devices and other equipment ( for example, pressure- 
reducing devices ) within the flow line. 

NOTE — The flow of a liquefied gas will be a two 
phase phenomenon, the fluid consisting of a mixture 
of liquid and vapour, the proportions of which are 
dependent on pressure and temperature. The pressure 
drop is non-linear, with an increasing rate of pressure 
loss as the line pressure reduces by pipe friction. 

11.4 Pressure Drop 

The pressure drop shall be calculated using two phase 
How equations for liquefied gases and single phase 
flow equations for non-liquefied gases. 

NOTE — These equations use friction factors and 
constants dependent on pressure and density 
obtained empirically. As the equations cannot be solved 
directly, a computer programme is usually used to 
assist with the large number of iterative calculations 
in which pipe and nozzle sizes and if appropriate, 
size of pressure reducing devices, are selected within 
prescribed pressure losses. 

11.5 Valves and Fitting 

Valves and fittings shall be rated for resistance 
coefficient or equivalent length in terms of pipe, 
or tubing sizes with which they will be used. 
The equivalent length of the cylinder valves 
shall be listed and shall include siphon tube ( where 
fitted ), valve, discharge head and flexible 

11.6 Piping Length 

The piping length and nozzle and fitting orientation 
shall be in accordance with the manufacturer's 
approved manual to ensure proper system 

11.7 Drawings 

If the final installation varies from the prepared 
drawings and calculations new 'as- built' drawings 
and calculations shall be prepared. 

11.8 Liquefied Gases ( Specific Requirements ) 

11.8.1 Allowance shall be made for changes in 
elevation as specified in the relevant standard 
relating to the specific agent. 

U.8.2 Minimum discharge rate for liquefied agents 
shall be sufficient to maintain the velocity required 
for turbulent flow to prevent separation. 

NOTE — I f turbulent flow is not maintained, separation 
of the liquid and.gaseous phases will occur, which can 
lead to unpredictable How characteristics. 

11.8.3 For information on two-phase flow for liquefied 
halocarbon gases ( see Annex E ). 



12.1 General 

All agents are suitable for use in both engineered 
central storage, system and pre-engineered 
( modular or packaged ) systems, as described 
in 12.2 and 12.3. 

12.2 Engineered 

An engineered system uses large storage 
containers installed in central location. The 
containers are manifold together and a single 
pipe feeds the nozzle located inside the 


IS 15493 : 2004 

hazard area. Predicting pipe pressure losses and 
designing nozzle orifice sizes required complex 
flow calculations for both agent and nitrogen 
phases ( in case of halocarbon gases ) and for 
agent ( in case of line gases ), which takes into 
account the minimum and maximum volumes or the 

12.3 Pre-engineered 

A pre-engineered system involves a single 
container the maximum of two nozzles and a small 
piping network. This system can be multiplied to 
cover larger volume areas. The larger area is viewed 
as a number of smaller areas each protected by a 
single modular unit. 


Physical properties of inert gas and halocarbon 
agents are shown in the Tables 9 and 10. 


14.1 AH persons who may be expected to operate, 
maintain, test or inspect fire extinguishing systems 
shall be kept continuously and adequately trained in 
the functions they are expected to perform. 

14.2 Personal working in an enclosure protected 
by or gaseous extinguishant shall be trained and 
kept fully conversant with the operation and use 
of the system, particularly regarding safety 

Table 9 Physical Properties of Inert Gas Agents 


SI No. 















Molecular weight 







Boiling point at 760 mm Hg 







Freezing point 







Critical temperature 







Critical pressure 


4 903 

3 399 


4 150 


Specific heat, vapour at 
constant pressure ( 1 atm ) 
and 25°C 







Heat of vaporization at 
boiling point 







Relative dielectric strength 
at 1 atm at 734 mm Hg, 
25°C(N 2 =1.0) 







Solubility of water in agent 
at 25°C 



0.001 3 



IS 15493 : 2004 

Table 10 Physical Properties of Clean Halocarbon Agents 

( Clause 1 3 ) 

SI No. 



HCFC Blend A 

HFC 227ca 







Molecular weight 





Boiling point at 760 mm Hg 





Freezing point 





Critical temperature 





Critical pressure 


6 647 

2 912 


Critical volume 





Critical density 

kg/m 3 




Specific heat, liquid at 25°C 





Specific heat vapour at constant pressure 
( 1 atm ) and 25°C 





Heat of vaporization at boiling point 
at 25°C 





Thermal conductivity of liquid at 25°C 





Viscosity, liquid at 25°C 





Relative dielectric strength at 1 atm at 
734 mm Hg, 25°C ( N 2 = 1.0) 





Solubility of water in agent at 21°C 


0.12 percent 
by weight 

0.006 percent 
by weight 

IS No. 


2189: 1999 


( Clause 2 ) 



Mild steel tubes, tubuiars and 
other wrought steel fittings: 
Part 2 Mild steel tubuiars and 
other wrought steel pipe fittings 
(fourth revision ) 

Selection, installation and 
maintenance of automatic fire 
detection and alarm system — 
Code of practice 

IS No. 

SP 30: 1985 



Specification for steel pipes for 
hydraulic purposes 

National Electrical Code 

Inspection and maintenance of 
gaseous fire extinguishing 
systems — Code of practice 


IS 15493: 2004 

( Clause 6.1 ) 



S3- 1 Any hazard to personnel created by the 
discharge of gaseous extinguishants shall be 
considered in the design of the system, in particular 
with reference to the hazards associated with 
particular extinguishants in the other standards of 
clean agents. Unnecessary exposure to all gaseous 
extinguishants shall be avoided. 

B-2 The decomposition products generated by the 
clean agent breaking down in the presence of very 
high amounts of heat can be hazardous. All of the 
present halocarbon agents contain fluorine. In the 
presence of available hydrogen ( from water vapour, 
or the combustion process itself ), the main 
decomposition product is hydrogen fluoride ( HF ). 

B-3 These decomposition products have a sharp, 
acrid odour, even in minute concentrations of only a 
few parts per million. This characteristic provides a 
built-in warning system for the agent, but at the same 
time creates a noxious, irritating atmosphere for those 
who must enter the hazard following a fire. 

B-4 The amount of agent that can be expected to 
decompose in extinguishing a fire depends -to a 
large extent on the size of the fire, the particular 
clean agent, the concentration of the agent, and the 
length of time the agent is in contact with the 
flame or heated surface. If there is a very rapid 
build-up of concentration to the critical value, then 
the fire will be extinguished quickly and the 
decomposition will be limited to the minimum 
possible with that agent. Should that agent's 
specific composition be such that it could 
generate large quantities of decomposition 
products, and the time to achieve the critical value is 
lengthy, then the quantity of decomposition 
products can be quite great. The actual concentration 
of the decomposition products then depends on 
the volume of the room in which the fire was burning 
and on the degree of mixing and ventilation. 

B-5 Although the vapour from halocarbon gas has 
low toxicity, the decomposition products can be 
very hazardous. The most widely accepted theory is 

that the vapour must decompose before the agent 
can inhibit the combustion reaction. Decomposition 
takes place on exposure to a flame or to a hot surface 
at a temperature above 480°C. In the presence of 
available hydrogen ( from water vapour or the 
combustion process itself), the main decomposition 
product is hydrogen fluoride ( HF ). 

B-6 The decomposition products of halocarbon 
agents have a characteristic sharp acrid odour, even 
in minute concentrations of only a few parts per 
million. This characteristic provides a built-in warning 
system for the extinguishant, but at the same time 
creates a noxious, irritating atmosphere for those who 
have to enter the enclosure following a fire. The actual 
concentration of the decomposition products 
depends on the volume of the enclosure in which 
fire is burning and the degree of mixing and 

B-7 Longer exposure of the vapour to tempera- 
tures in excess of 482°C would produce greater 
concentrations of these gases. The type and sensi- 
tivity of detection, coupled with the rate of discharge, 
should be selected to minimize the exposure time of 
the vapours to the elevated temperature if the 
concentration of breakdown products is to be 
minimized. In most cases, the area would be untenable 
for human occupancy due to the heat and breakdown 
products of the fire itself. 

B-8 Clearly, longer exposure of the agent to high 
temperatures would produce greater concentrations 
of these gases. The type and sensitivity of detection, 
coupled with the rate of discharge, should be selected 
to minimize the exposure time of the agent to the 
elevated temperature if the concentration of the 
breakdown products is to be minimized. 

B-9 Non-liquefied agents do not decompose 
measurably in extinguishing a fire. As such, toxic or 
corrosive decomposition products are not found. 
However, breakdown products of the fire like carbon 
monoxide itself can still be substantial and could 
make the area untenable for human occupancy. 


IS 15493 : 2004 


(Clause 10.10) 



This clause sets out a procedure to determine 
compliance of the gaseous total flooding system 
with the requirements for discharge time, concentration 
and holding time. 


The system is operated, discharge time is measured 
and concentration readings are taken at a specified 
height at nominated periods. 


The test medium shall be the concerned halocarbon 
or inert gas. 


The following apparatus is required: 

a) A chart recorder type concentration meter 
calibrated in strict accordance with the 
manufacturer's instructions, 

b) A suitable time-measuring device, and 

c) Temperature-measuring equipment. 


The procedure shall be as follows: 

a) Ensure that the preliminary checks, in 
accordance with respective standard 
pertaining to gaseous fire extinguishing 
system have been completed, 

b) Electrically isolate all flooding systems 
serving adjacent enclosures, 

c) 1) Concentration measurements should 

be made at a minimum of three points, 
one at the highest hazard level, 

2) Locate sampling points in the enclosure 
at the specified heights ( see 10 ). Do 
not locate sampling points nearer than 
200 mm to ceiling unless the combustibles 
being protected extend within that area, 
in which case special design 
considerations may be necessary, 

3) If more than one space or compartment 
is being simultaneously protected, 
locate a sampling point in each space in 
accordance with the above criteria. 
Additional sampling points may be 

required by the appropriate authority, 

4) Where the geometry of the enclosure 
does not lend itself to sampling in the 
above manner, take a minimum of three 
samples at locations agreed upon by the 
appropriate authority. 

d) Set the continuous chart recorder type 
concentration meter for the agent concerned 
and check that the meter is calibrated in 
accordance with the manufacturer's 
instructions so that it will record 
concentration levels at each sampling 
point for 10 min from commencement of 

e) Record temperature in enclosure, 

f) Ensure that plant which is capable of 
affecting system performance, for example, 
air-handfing plant is in its normal operating 

g) Activate the system and record the discharge 
time (see 1! ), and 

h) Record concentration readings and holding 
times (see 11 ). 


Restore all systems to a fully operational status. 


The following shall be reported: 

a) 1) installation, designer and contractor; 

2) enclosure identification; 

3) enclosure temperature prior to discharge; 

4) design concentration; and 

5) position of sampling points. 

b) Date and time of test, 

c) Discharge time, 

d) Concentrations at each sampling point 
at I and 10 min from the commencement of 
discharge, and 

e) System deficiencies. 

Cross-check various observed parameters with the 
respective operating clauses are in conformity 


IS 15493: 2004 


(Clause 10A0) 




D-l.l Principle 

A fan is temporarily located within an access 
opening to pressurize and depressurize the enclosure. 
A series of pressure and air flow measurements is 
made from which the leakage characteristics of the 
enclosure; are established. 

The predicted hold time is calculated using 
these leakage characteristics on the following 

a) That leakage occurs under the worst 
conditions, that is, when one-half of the 
effective leakage area is at the maximum 
enclosure height and represents the 
inward leakage of air, and the other half ( the 
lower leakage area ) of the total effective 
leakage area is at the lowest point in the 
enclosure and represents the outward 
leakage of extinguishant/air, 

b) That all leak flow is one-dimensional, i.e. 
ignoring stream functions, 

c) That flow through any particular leak area 
is either into or out of the enclosure and 
either from or into an infinitely large space, 

d) That the system is at sea-level, at a 
temperature of 20°C, and atmospheric 
pressure of 1 .0 1 3 bar absolute, and 

e) An enclosure integrity test is deemed 
successful when at least 80 percent of 
the design concentration is available 
within the enclosure at the expiry of 

D-l. 2 Apparatus 

a) Fan unit, consisting of a frame which will fit 
into and seal an access opening in the 
enclosure, and one or more variable speed 
fans, with low flow facilities, capable of 
giving a differential pressure of not less 
than 25 Pa across the enclosure boundary, 

b) Two pressure-measuring devices, one to 
measure enclosure differential pressure 
and one to measure fan flow pressure, 

c) Flexible tubing, for 



pressure-measuring devices, 

d) Chemical smoke pencils and/or smoke 

Two thermometers, to measure ambient 
temperatures, and 

f) Signs, reading "DO NOT OPEN — 

NOTE — Additional apparatus, such as measuring 
tapes, torches, ladders, tools to remove floor and ceiling 
tiles, computer or other calculating device, may be 

"D-l ,3 Calibration of Apparatus 

a) Fan Unit — Calibrate the fan unit at the 
intervals and by the method recommended 
by the manufacturer. Keep records and, where 
appropriate, calibration certificates. Use a 
flow meter accurate to ± 5 percent and a 
pressure-measuring device accurate to ± I Pa. 

b) Pressure-Measifring Devices — The 
pressure-measuring devices shall be 
calibrated not more than 1 2 months before 
a test. Records shall be maintained and, 
where appropriate, calibration certificates. 

If inclined manometers are used, change 
the fluid not more than 3 months before the 
test. Level and zero inclined manometers 
before each test. 

D-L4 Preliminary Preparation 

a) Obtain a description from the user of the 
air-handling equipment and extinguishant- 
extraction systems in the enclosure, 

b) Check for the following: 

1) raised platform floors and false ceiling 

2) visually obvious leaks in the enclosure; 

3) adequate return paths outside the 
enclosure between all leaks and the fan 
unit; and 

4) conflicting activities in and around the 

c) Provide the following information to the user: 

1) a description of the test; 

2) the time required to complete the test; 

3) what assistance will be needed from the 
user's staff; and 

4) Information on any necessary 
disturbance to the building or its 
services during the test ( for example, 


18 15493:2004 

removal of floor or ceiling tiles, 
shutdown of air-handling systems, 
holding doors open and/or shut ). 

D-1.5 Evaluation of Enclosure 

Obtain or prepare a sketch plan showing the walls, 
the location of the door and other openings through 
which air will flow during the test, and the location 
of any ducts penetrating the enclosure, and any 
dampers in the ducts. Show the status ( that is, 
whether open or closed when the extinguishant 
system is discharged ) of each door, hatch and 
damper, and which access opening(s) is (are) to be 
used for the fan unit. 

Show the location of floor and sink drains, 

D-1.6 Measurement of Enclosure 

Measure the protected enclosure volume as necessary 
and record the following; 

a) Overall height of the protected enclosure, 

b) Height of the highest hazard in the 
enclosure, and 

c) Gross volume of the protected enclosure. 
D-1.7 Test Procedure 

a) Preparation for Test 

t) Advise supervisory personnel in the 
area of the test. 

2) Remove papers and objects likely to 
be disturbed by the turbulence from the 

3) Block open sufficient doors outside 
the enclosure envelope to provide an 
adequate return path for air between 
the fan unit and the enclosure leaks, 
while correcting any breach of any 
requirements of the facility, including 
requirements for security, fire protection 
and environmental boundaries. 

4) Using the sketch plan ( see D-1.5 ), set 
all air-handling equipment and 
extinguishant-extraction systems to 
the state they would be in at the time 
of extinguishant system discharge, 
except for the following: 

i) Recirculating air-handling 

equipment without fresh air make- 
up which does not give a bias 
pressure across the enclosure 
boundary or otherwise preclude 
accurate testing, and which would 
be shut down on extinguishant 
discharge, may be left operating 

during the test if this is needed 
to avoid temperature build-up 
in equipment such as computers; 

ii) Recirculating air-handling 

equipment which would continue 
to operate on extinguishant 
discharge should be shut down, if 
it creates excessive bias pressure. 

5) Post the appropriate signs on doors 

6) Open doors and remove floor or ceiling 
tiles within the extinguishant- protected 
portions of the enclosure envelope so 
that the extinguishant- protected volume 
is treated as one space. Do not remove 
false ceiling tiles if the volume above the 
false ceiling is not protected with 

7) Close all doors and windows in the 
enclosure envelope. 

8) Check that liquid traps in the floor and 
sink drains are sealed with liquid. 

b) Setting up Door Fan Unit 

1) Set up the fan unit in an access opening 
leading from the enclosure into the 
largest volume of building space 
which will complete the air-flow path 
from the fan, via the enclosure, leaks and 
building space back to the fan. 

2) Gently blow into or suck from the 
flexible tubing so that the readings of 
the pressure-measuring devices 
traverse the full scale. Hold the 
maximum reading for not less than 10 s. 

Release the pressure and zero the 

3) Connect the enclosure differential 
pressure-measuring device. Ensure 
that the open ends of the flexible 
tubing near the fan unit are away 
from its air stream path and any other 
air flows which might affect the 

4) Use the fan(s) to raise or lower the 
pressure of the enclosure by 
approximately 15 Pa. Check all 
dampers with smoke and ensure that 
they are closing properly. Check doors 
and hatches and ensure correct 
closure. Inspect the wall perimeter 
( above and below any false floor ) and 
the floor slab for any major leaks and 
note their size and location. 


IS 15493:2004 

c) Measurement of Bias Pressure 

1) Seal the fan unit inlet or outlet and, without 
the fan(s) operating, observe the 
enclosure differential pressure-measuring 
device for at least 30 s. 

2) If a bias pressure is indicated, use smoke 
to detect the consequent air flow and its 
direction. If the existence of a bias 
pressure is confirmed, record the 
pressure-measuring device reading as the 
bias pressure (Pb). 

3) If the enclosure is large, or if the bias 
pressure is largely caused by wind or 
stack effects, repeat the measurement at 
one or more different access openings. 
Record all the values measured and use 
the largest positive value ( or if only 
negative values are recorded, the value 
closest to zero ) as the bias pressure. 

A bias pressure as low as 0.5 Pa can affect the accuracy 
of the test result. If the bias pressure has a numerical 
value greater than 25 percent of fire extinguishant/ 
air column pressure, thenthe hold time is likely to be 
low and the enclosure may not hold the specified 
extinguishant concentration. The source of the 
excessive bias pressure should be identified and, if 
possible, permanently reduced. 

In the event of fluctuating bias pressures ( such as 
those created by wind effects ), it may not be possible 
to achieve the necessary correlation accuracy in the 
fan test results. These fluctuating pressures may need 
to be eliminated before an accurate fan test can be 
carried out. 

d) Measurement of Leakage Rate 

1) Measure the air temperature inside 
the enclosure, T e and measure the air 
temperature outside the enclosure T , at 
several points. If the location of leaks 
is not known, use the average value; 
otherwise, use the average value 
weighed according to the known 
location of the leaks. 

2) Unseal the fan inlet or outlet and 
connect the fan flow pressure- measuring 

3) Use the fan unit to depressurize the 
enclosure to the maximum extent, but 
by not more than 60 Pa. Allow the 
enclosure differential pressure 
measuring reading to stabilize ( which 
may take up to 30 s ) and record the value 
( P f + P b ) which will be negative. Repeat 
at not less than four more fan unit 
flow rates to give five readings more 

or less evenly spaced over the range 
down to 10 Pa. 

4) Use the fan unit to pressurize the 
enclosure and repeat the procedure 
of (d) (iii). Again record the value of 
( P r + P b ), which will be positive. 

NOTE — For calculation purpose, either P f or P b or 
the average of the two can be taken. 


D-2.1 Notations 

Q = air leakage rate, in m 3 /s; 

C - flow coefficient; 

P = pressure within enclosure, in Pa; 

N - slope of the graph; 

R M - density of agent /air Mixture, in kg/m 3 ; 

Agent Density, kg/m 3 

Air 1202 

HCFCBIendA 3.84 

HFC-227ea 7.26 

IG-541 1.41 

IG-55 1.41 

R A = density of air, in kg/m 3 ; 
= density of agent, in kg/m 3 ; 


P M = agent/Air column pressure, in Pascal 

G = gravitational acceleration, 9.81 m/s 2 ; 
H Q - total height of the enclosure, in m; 

H = minimum acceptable height in the 
enclosure, in m; 

A - area of the enclosure, in m 2 ; 

V - volume of the enclosure, in m 3 ; 

Q^ = uncorrected agent/air mixture leakage 
rate, in m 3 /s; 

Q u = corrected agent/air mixture leakage rate, 
in mVs; 

T L = temperature within the enclosure, in °C; 

7* F - temperature outside the enclosure, in °C; 

ELA = equivalent leakage area, in m 2 ; 

K = discharge coefficient ( 0.61 to 
I depending upon nature of leakage 
openings ); 

TLA = total leakage area, in m 2 ; 

LLF = lower leak fraction; 

ALL = area of lower leaks, in m 2 ; 

c ~ agent concentration, in percent; 


IS 15493: 2004 

C p - pass concentration in percent 
( 80 percent of the design agent 
concentration ); 

C 3 m equation simplification constant; 

C 4 = equation simplification constant; and 

T - retention time of pass concentration 
(C ) within the enclosure, in seconds. 

D-2,2 After pressurizing ( depressurizing ) the 
enclosure to various pressures, corresponding 
flow rates in //s for each room pressure shall be 
recorded wherefrom the flow at 1 Pa pressure i$ 
determined. This value (C) is deemed as flow 
coefficient ( constant ) for the purpose of 

The formula establishing a relation between flow 
and the pressure is Q » CP N where Q ~ Air leakage 
rate, in m 3 /s, C - Flow coefficient, P = Pressure within 
enclosure in Pa and N - Slope of the graph. 

NOTE — The value of N can be determined by 
substituting observed values for Q 9 P and C in the above 

D-2.3 The next step will be to determine the density 
of agent/air mixture ( R M ): 

RM= — + — kg/m 3 



D-2.4 The next step will be to determine the agent/ 
air column pressure (PM); 

D-2.5 The next step will be to determine the 
uncorrected agent/air mixture leakage rate: 

m = (C)(/> M ) N ni 3 /s 

D-2.6 The next step will be to determine the corrected 

agent/air mixture leakage rate: 

* M (r p -f273) 

D-2,7 The next step will be to determine the equivalent 
leakage area ( ELA ) : 

( 1.271 )(0 M ) 




D-2.8 The next step will be to determine the total 
leakage area ( TLA ) : 

TLA = (K)(ELA)m 2 

D-2.9 The next step will be to determine the lower 
leak fraction (LLF) : 

LLF = 



D-2J The next step will be to determine the retention 
time ( T) : 

(l-N)(C 3 )(LLF)(TLA) 

c 3 = 


:/? m) + (^)[ttzzf] 

2 ( Static pressure inside enclosure ) 

c 4 = — 

V M 


1 If static pressure is negative, then treat it as zero. 

2 If static pressure is positive, then consider actual 


IS 15493:2004 


(Clause 11.83) 


E-I As the extinguishant in the liquid phase flows 
from the storage container, the pressure drops or 
recedes. The pressure recession varies with 
container fill density. It is assumed that there was 
thermodynamic equilibrium between the liquid and 
vapour phases in the storage container. In actual tests, 
it has been noted that there is a sharp drop in pressure 
during the initial rush of liquid into the distribution 
system. This is due to a lag between the pressure 
drop and the onset of boiling in the container, As boiling 
commences, the pressure returns to the pressures 
shown on the curves for respective gaseous 
extinguishants representing the calculated pressure 
in the storage container versus the percentage 
discharge of extinguishant from the container for both 
2.5 MPa and 4.2 MPa systems. 


Agent flows through the distribution system in 
both liquid and vapour phase. As the liquid phase 
flows through the distribution system the 
pressure continues to drop, causing the liquid to boil. 
The volume of the vapour phase increases with the 
decreasing pressure and hence the density of the 
mixture drops. To maintain a constant flow rate, the 
speed through the distribution system must 
continuously increase down the pipe work. The 
pressure drop for a given flow rate is not linear, as it 
is with water, but is variable along the pipe. 



Using the thermodynamic properties of the 
Agent, including the nitrogen used for super- 
pressurization, the density of the two-phase mixture 
in the distribution system can be calculated. The 
density of the Agent leaving the storage container 
varies over the course of the discharge. The density 
is lowest at the start of discharge and increases 
until the last of the liquid leaves the container. 


The drop in container pressure as the Agent flows 
from the container causes remaining Agent in the 
container to cool. As a result, liquid that is below 
ambient temperature is introduced to the distribution 
system. During a system discharge the temperature 
of the Agent leaving the storage container recedes 
as a function of instantaneous container pressure. 


At the start of discharge virtually all the liquid phase 

Agent entering the distribution system is vaporized 
before it reaches the nozzles, due to heating by 
the pipe work and the initial low pressure in the 
system. The initial vaporization limits the flow of 
Agent through the distribution system because the 
mass flow of vapour is much lower than that of liquid. 


There is a signifrcant delay between the opening of 
the discharge valve and the first appearance of liquid 
at the nozzles. Some of the delay is due to the flow 
restriction presented by the container and distribution 
system, however much of delay is due to the initial 
vapour phase flow of the Agent. 


The flow of Agent in the distribution system is a two- 
phase flow ( containing both liquid and vapour ). In 
a properly sized distribution system the flow will 
be highly turbulent throughout the system and the 
two phases will mix homogeneously. If the pipes are 
too big the phases may tend to separate, which can 
cause a variety of flow problems and can in some cases 
result in a reduced flow rate. 


Pressure at the nozzle is not constant throughout 
discharge because the pressure in the storage 
container is constantly decreasing. If one were to 
attempt manual calculation it would be desirable to 
use an average pressure condition. It is difficult to 
arrive at an average as the volume of piping has a 
marked effect on the average nozzle ( pressure, 
density and velocity conditions ), all of which, have 
a marked effect on discharge quantities and times. 


The nozzle pressure used for calculations is the 
pressure when half the liquid phase has been 
discharged from the nozzle. The timing of this is used 
to calculate an average pressure drop in the distribution 
system. To calculate the correct storage container 
pressure, allowance must be made for the amount of 
liquid in the piping system. 


The points outlined above are taken into 
consideration to calculate the average container 
pressure during discharge. The ratio of the pipe 
volume to the volume of Agent supply expanded 
under flowing conditions varies with average 
container pressure. The former quantity shall be 
referred to as percent-in~the-pipe. 


Bureau of Indian Standards 

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote 
harmonious development of the activities of standardization, marking and quality certification of goods and 
attending to connected matters in the country. 


BIS has the copyright of all its publications. No part of these publications may be reproduced in any form 
without the prior permission in writing of BIS. This doesnot preclude the free use, in the course of implementing 
the standard, of necessary details, such as symbols and sizes, type or grade designations. Enquiries relating 
to copyright be addressed to the Director (Publications), BIS. 

Review of Indian Standards 

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed 
periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are 
needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards 
should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue 
of W B1S Catalogue" and ^Standards : Monthly Additions'. 

This Indian Standard has been developed from Doc : No. CED 22(7011 ). 

Amendments Issued Since Publication 
Amend No. Date of Issue Text Affected 


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